1956 322 Nailhead oversize .060 pistons??

**OzBuick** · 07-13-2011, 03:31 AM

I have a 1956 322 Nailhead currently at .030 oversize. Has sustained damage to a couple of cylinders, engine builder wants to bore to .060 oversize - is it ok to do this?? can anyone advise please??

**DocModisett** · 07-13-2011, 04:16 AM

I would think that it would be better to sleeve the 2 cyls. back to specs than to over bore all the cyls. that much.... because, when you overbore that much the engine is going to tend to overheat a lot more , a lot quicker.... btw be sure to clean the radiator while you are doing the engine work....

**telriv** · 07-13-2011, 07:23 PM

Have the block bores sonic tested for thickness. Then you'll know if .060" overbore is going to hold up. If a little too thin you could add epoxy to the bottom of the big freeze plugs on the side of the block to help stabilize the bottom end. This will also add longevity to the rebuild. This has NO effect on coolant temps. In comparison to the cost of a rebuild it's cheap insurance. Normally in the $75.00-$125.00 range. With thinner cylinder walls the old adage of overheating is a myth. Thinner walls pass/transfer heat faster to the cooling system. Sorry to dis-agree Doc.

**DocModisett** · 07-14-2011, 03:56 AM

Wellllll, Tom,,,, ole pard,,, I have to disagree with your disagree

.....the reason that I told him that was that I had a bbb in my skylark with a gooood radiator in it , shroud , big fan and all that ,,, it ran cool, untill I bored it ,060 over, and after that , about 2 good runs and it would be hot,,, 3 runs and it was really hot.... just experience,,, just experience....he may have to put a bigger radiator on to handle the cooling... Me thinks....

but I dont care if you disagree, Tom,,, I like you anyway.....

**telriv** · 07-14-2011, 06:45 PM

And I love you too Doc!!!!

**BigRivy** · 07-14-2011, 09:40 PM

I've been in the automotive machine business for 25 years and I have to say I am siding with TelRiv. Boring an engine does not make them Heat! If it does I'd say you just haven't found your problem yet. I was at an engine building conference several years ago and had a conversation about this with famed sprint car engine builder Earl Gaurte, Smokey Yunick was there too. He said often when building ultra high output non traditional engines with thick walls that they often had to bore them to get them to cool properly. The thick walls were too much of a heat dam. When using factory issued race blocks the engineers take this into consideration and design blocks with the best thickness for strength vs. cooling. Nothing against you Doc, just stating my experience.

**DocModisett** · 07-15-2011, 03:47 AM

I know when I am out voted.....

I am just gonna go out and set down under a tree and mutter in my moustache.....

Tom,,,, Bigrivy,,,, engine heat,,,, Tom

**OzBuick** · 07-16-2011, 08:21 PM

thankyou all for your information and advice. HE is actually a SHE

... that owns this beautiful engine and the 1955 Buick that it will go back into. I think my preference is to have the 2 cylinders resleeved and bore to original .030 oversize .... but if this is not possible I will be happy with the .060 now that I am armed with new information. I will take Doc's advice and have the radiator looked at ... can't hurt given that the engine is pulled apart anyway!!

**DocModisett** · 07-17-2011, 05:28 AM

If you do just the 2 cyls and bring them back to the same size as the rest,,, the engine block will last longer.... and nailhead blocks are getting harder to find.... personally I would go with a new set of pistons and rings if the engine had a lot of miles on it.... they are the weak link on a nailhead engine.... or at the very least go over the old pistons with a magnifying glass to be sure none of them is cracked anywhere.... I have sleeved several engines and never had a problem with them....